The invention relates to a wear-resistant surface armoring for the rolls of high-pressure roll presses for the pressure disintegration of granular material, having a plurality of nap bolts that are made of hard material and are mounted in corresponding recesses of the roll body, which bolts project from the roll body and form between themselves pockets for the acceptance of pressed-together fine granular material.
In rolling crushers and roll mills, brittle material to be crushed is drawn into the nip that separates the two rotatably mounted rolls from one another, which rolls can be rotated in directions opposed to one another, and is there subjected to pressure disintegration. What is referred to as interparticle crushing in the nip of a high-pressure roll press is also known, in which the individual particles of the material to be crushed, drawn into the nip by friction, are mutually crushed in a bed of material, i.e., in a grist pressed together between the two roll surfaces with the application of a high pressure. Of course, the roll surfaces are thereby exposed to extraordinarily high stress and a high degree of wear.
It is therefore known to make the surfaces of interparticle crushing roll presses resistant to wear by mounting a plurality of pin-shaped nap bolts at spaced intervals in blind holes in the roll body, which bolts project in the manner of spikes from the holes in the roll body (EP-B-0 516 952, U.S. Pat. No. 5,269,477, FIG. 2). The pin-shaped nap bolts should thereby project outward from the roll surface at such a height, and should be arranged at such a spacing from one another, that during operation of the roll press the intermediate spaces or pockets on the roll surface between the pin-shaped nap bolts remain filled with the pressed-together fine granular material, forming what is known as an autogenous wear protection for the roll surfaces. However, during operation of a high-pressure roll press armored in this way, the danger cannot be entirely excluded that damages can arise in the coating surface of the roll by means of the formation of fissures as a result of the high pressure that acts on the notch points present in the recesses/bores of the roll body via the pin-shaped nap bolts, in particular given laterally acting forces, which damages cause a shortening of the serviceable life of the armoring.
It has also already been proposed (EP-A-0 578 239) in rolled armorings with pin-shaped nap bolts of the type described above, to fashion the radially inner (lower) ends of the nap bolts with a hemispherical or dome shape, and to let the nap bolts be supported with these shaped ends on correspondingly hemispherical blind hole ends of the recesses provided in the roll body, in order to reduce the influence of notch tensions. However, the expense for the manufacture of dome-shaped blind hole ends and bolt ends of this sort is not inconsiderable; a snug seating of the bolt end in the correspondingly shaped blind hole base must be ensured; and, moreover, the pin-shaped nap bolt with its hemispherical end in its blind hole can tend to tip under the action of the high roll pressure force. Moreover, with the use of previously known nap bolts, due to their relatively small diameter, it cannot be excluded that the material to be processed becomes "coiled around" the bolts during roll press operation, particularly in case of a higher degree of dampness of the material to be processed. This has an adverse effect on the dispersion characteristic of the material being pressed, and can cause erosion of the base material between the nap bolts.